gistfile1.rb

# fguillen 2009-06-25: 
# inspired on: http://github.com/patientslikeme/migration_helpers/tree/
#
#  add a foreign key constraint
#  add_foreign_key 'books', 'author_id', 'authors'
#
class ActiveRecord::Migration
  def self.add_foreign_key(
    table, 
    target_table, 
    column = "#{target_table.singularize}_id", 
    target_column = "id", 
    constraint_name = "fk_#{table.to_s}_#{target_table.to_s}"
  )
    execute( 
      "ALTER TABLE #{table.to_s}" +
      " ADD CONSTRAINT #{constraint_name.to_s}" +
      " FOREIGN KEY (#{column.to_s})" +
      " REFERENCES #{target_table.to_s} (#{target_column.to_s});"
    )
  end

  def self.remove_foreign_key(
    table, 
    target_table, 
    constraint_name = "fk_#{table.to_s}_#{target_table.to_s}"
  )
    execute "ALTER TABLE #{table.to_s} DROP FOREIGN KEY #{constraint_name};"
  end
  
end